Vegetables such as cucumber which are commercially available as materials for light pickles are shipped after mixed with 3% to 5% salt and pickled with seasoning for several hours, and an amount of shipment thereof is increasing year and year as fresh fibrous food having good resistance to the teeth and clear green tint. On the other hand, as material for green salad, such vegetables are shipped after and sterilized
Therefore, it can be said that such commercially available material vegetables for light pickles and green salad are accepted by consumers to some extent. However, since a preservable time of them is usually about one week after shipment, the preservability thereof is poor and so manufacturers must produce and ship them while estimating the marketability thereof. Therefore, it is very difficult for the manufacturers and traders to stably produce and sell them efficiently through years due to change of planting area, climate, unstable factors such as quality and cost caused by seasonal shift of planting area and heating cost for heating green houses in winter season and, so a novel method for storing fresh vegetables has been highly required.
As one of proposals, an attempt of freeze-preservation of material vegetables for such green salad and light pickles as mentioned above has been made. However, since the water content of cells of such material vegetables is crystallized when frozen, tissue thereof is damaged when defrozen, resulting in dripping of the vegetables, degradation of resistance to the teeth and rapid degradation of freshness. This can not be completely prevented by a conventional rapid nitrogen gas freezing technique or a conventional freezing method in which water content of the vegetable is removed by using salts of high concentration and then the vegetable are frozen.
An object of the present invention is to provide a method of freeze-preserving vegetables by not merely rapidly freezing them as in the conventional method but adding substances which remove water from cells of the vegetables and block crystallization of water molecules to the vegetables.
Another object of the present invention is to provide a freeze preservation method of vegetables which can restrict a growth of water crystals in cells of vegetables to prevent cell membranes, cell walls and intracell organs of vegetables from being destroyed when the vegetables are frozen and make the vegetables usable as materials for light pickles without necessity of any post processing thereof immediately after they are defrozen and usable as materials for fresh green salad by supplementing water to cells of the defrozen vegetables to restore their plasma and which can widen the shipping condition of fresh vegetables indispensable for human being to stabilize the food situation of human life.